anhydrite screeds !!!!!!!!!!

[terry the tiler]

Hi all , Question about anhydrite screeds iam afraid ! lol.., how do i no if its a anhydrite screed or not ? so confused about screeds!! and y do you have to use anhydrous screed ? whats the benefit over latex ?

[garythetiler]

Ajax is the expert on anhydrite screed on the forum ,but in laymans terms anhydrite screeds are gypsum based rather than cement based ,they are normally flowable and pumped in and give a very level flat finish when done right ,these types of screeds need different type of preparation to conventional sand and cement based floors and the surface latience is normally ground off prior to tiling ,anhydrite screeds are not normally recommended for wet areas due to their chemical compostion also they must be primed prior to the installation of tiles as most cement based adhesive react badly to this kind of surface, anhydrite screeds are extremely popular in europe and are slowly becoming popular here ,if you are unsure about a substrate you are tiling on whether its anhydrite or not i would recommend decoupling it with a matting system, hope this helps, i am sure ajax will be along shortly to clear up any confusion

[TF Ed]

ajax is away for another week or so....
he's stage managing a play.

ed

[Phil Hobson]

I think Gary has done an exelent job standing in for Ajax nice one Gary

[Scott]

Good question and one i was pondering today whilst digging my hall screed up to dig out a pad foundation!

So can you tell visually if its anhydrite or do they look the same?

[terry the tiler]

Ajax is the expert on anhydrite screed on the forum ,but in laymans terms anhydrite screeds are gypsum based rather than cement based ,they are normally flowable and pumped in and give a very level flat finish when done right ,these types of screeds need different type of preparation to conventional sand and cement based floors and the surface latience is normally ground off prior to tiling ,anhydrite screeds are not normally recommended for wet areas due to their chemical compostion also they must be primed prior to the installation of tiles as most cement based adhesive react badly to this kind of surface, anhydrite screeds are extremely popular in europe and are slowly becoming popular here ,if you are unsure about a substrate you are tiling on whether its anhydrite or not i would recommend decoupling it with a matting system, hope this helps, i am sure ajax will be along shortly to clear up any confusion

thanks 4 that !! v helpful . is there any way of knowing if its a anhydrite screed ? is it a different colour or texture ? just wondering if i went to price a job up that was screeded how would i tell if its a anhydrite screed or not ?

[Phil Hobson]

Again Ajax is the man for this, but anhydrite tends to be less coarse than sand and cement. Sand and cement screed is made with grit sand (zone two) it used to be called. Hurry back Ajax

[Dave]

Anhydrite screeds will be lighter in colour to a cement based screed, they will normally be a milky off white colour and quite smooth in texture.

You also might notice that it is laid in bigger area's without expansion joints compared to a sand/cement screed.

The easiest way to tell is ask the client for the screed spec etc.

As for the reason for using an Anhydrite screed over a sand/cement screed is that it is a lot stronger structurally than a sand/cement screed, especially when it comes to in screed heating incorporated within the screed.

The neutron strength of an Anhydrite screeds is around 30+ neutrons to the sqr mtr and a sand/cement screed is only around 1 neutron per sqr mtr if i recall correct..Alan from lafarge will correct me if i am well out on that but after convo's with Alan on numerous occasions ,that is what i recall as to the strength differences.


You will also notice the extreme flatness of an Anhydrite screed...

I hope that info helps you out.

[Phil Hobson]

We do miss Ajax, but with Gary and Dave on hand, not as much

[andy8758]

How the world has changed.

My first venture into tiling was as a new home owner in the early 1980's. The choice of tiles was - 6" or (the new fangled and terribly modern) 150mm tiles being sold in the DIY sheds. You either tiled on plaster or cement. Sub-strata prep was largely unheard of. Adhesive was Unibond or (er) Great Mills own make. Oh it was all so easy.

Thank heavens for Tiling Forums in 21st Century. Everything is so complex now, you need an HND in chemistry to become a real professional tiler!

Fair play to all you guys with the experience the rest of us lack - anhydrite screeds? Whatever next!

[hillhead]

Anhydride screeds are poured i believe,they look a lot like a levelling compound i believe too.
I have come across this screed 3 times since last summer i think,lol.
I noticed how soft it is too?
I used a wire brush attachment on my grinder to scratch the surface off,primed with primer G and tiled away! no probs at all and so flat its unreal,it would make a bad tiler look good.....

[Phil Hobson]

How the world has changed.

My first venture into tiling was as a new home owner in the early 1980's. The choice of tiles was - 6" or (the new fangled and terribly modern) 150mm tiles being sold in the DIY sheds. You either tiled on plaster or cement. Sub-strata prep was largely unheard of. Adhesive was Unibond or (er) Great Mills own make. Oh it was all so easy.

Thank heavens for Tiling Forums in 21st Century. Everything is so complex now, you need an HND in chemistry to become a real professional tiler!

Fair play to all you guys with the experience the rest of us lack - anhydrite screeds? Whatever next!

Spot on there mate, I have often said we need to be chemist's as well as tilersgood job we like a challenge